Assembly Matrix
Manual Transmission Gears Parts 2025
Overview of assemblies, gear compatibility, spline types, and roller configurations.
‘Syracuse’ M20: The Wide-Ratio Benchmark
The Muncie M20 is a smooth-shifting, wide-ratio 4-speed — engineered for street cruising, restorations, and lighter builds. With global-quality components and AutoGear durability, it’s a modern classic ready for the road.
Whether you’re building a daily driver, a classic cruiser, or a period-correct muscle car, the M20 brings effortless shifts and long-lasting performance — all in the original Muncie footprint.
Why Choose the M20?
✅ Smooth, predictable RPM drop between shifts
✅ Supercase standard with 9310-equivalent countershaft
✅ OEM-friendly install footprint for easy retrofits
✅ Durable, quiet operation for road use
✅ Ideal for lighter builds or street-first restorations
Gear Ratio Packages
| Model | 1st Gear | 2nd Gear | 3rd Gear | 4th Gear | Best For |
|---|---|---|---|---|---|
| M20 | 2.521 | 1.880 | 1.461 | 1.00 | Street cruising & lighter loads |
Additional ratio codes available (314, 324, etc.) — Contact us to find your match.
Resources
View documents and resources related to this gearbox in the resource center.
View ResourcesThe Complete Guide
AutoGear Gearbox & Gearset Option Codes
Overview of assemblies, gear compatibility, spline types, and roller configurations.
Muncie M20 — Frequently Asked Questions
The Muncie M20 is a wide-ratio four-speed with the following gear set: 2.52:1 first, 1.88:1 second, 1.46:1 third, and 1.00:1 fourth. The wide spacing between gears works well with the broad torque curves of American V8s, which is why the M20 has always been the right call for street driving, daily drivers, and period-correct muscle car restorations.
Additional ratio codes are available. Call 315-471-8141 or submit an inquiry to find your match.
A 3.73 or 4.10 rear gear works well for street or moderate performance use. The right pairing depends on your full combination — engine torque curve, vehicle weight, tire height, and how you drive all factor in. A heavier car needs less rear gear to get moving; a lighter build can run tighter. When those pieces don't line up, the whole drivetrain feels off.
Not sure what ratio fits your build? Call 315-471-8141 or submit an inquiry.
The M20's gear ratios work for drag and track applications — the wide spacing can help off the line depending on your setup. The limitation is gear strength. The M20 wasn't built for the sustained stress of drag racing or strip use, and pushing it in that application puts the case and internals under load they weren't designed to handle.
If drag use is your goal and you want the same ratio in a stronger package, the AutoGear M23 is worth the conversation. Call 315-471-8141 or submit an inquiry.